Google Buzz Malware

"[Buzz] also gained unwanted attention from cybercriminals who already
used the service to spread a malware detected by Trend Micro as
WORM_PROLACO.AA."

"[It] installs Firefox extension and Firefox Security 2.0 by creating
specific files on affected systems. These extensions check the browser’s
address bar for specific strings related to googlesearchserver, search,
google.com, yahoo.com, bing.com, ask.com, and aol.com/aol/search?s_it.
If found, the malware loads a page which triggers the display of ads on
search results pages. The worm further spreads by sending email messages
to target addresses that it gathers from affected systems. It also drops
copies of itself in shared peer-to-peer (P2P) sharing folders."

Users should be wary of files and installable applications available on
social networking sites. Keeping your anti-virus and operating system
software up to date is critical in combating virii like this.